Because I can't be bothered to deal with cheats. They can take how many counter measures they can, but usually the cheats end up winning.
Don't want to deal with that on consoles.
What kind of cheating are you worried about, exactly? Have you experienced such cheating in a fighter online? Wouldn't it be obvious, thus bannable, or easy avoided?
Unless you're referring to in-game exploits, it's impossible to cheat on the PS4/XBO until and unless they have been exploited/hacked. The only exception is when a game allows you to import profile/stats from the PS3/X360 version (e.g. Diablo III).
Either way, my stance on this matter is that as long as console players are given the option to disable crossplay (already the case with SFV), it's all good.
You can use Cronus Max controller convertors on consoles to program long combos for use at the touch of a button, so this supposed cheating for an unfair advantage is just as possible on consoles,with no actual game hacking.